Method and apparatus for registration of location information of wireless devices in a wireless communication network supporting multicast calls

ABSTRACT

An apparatus and method for transmitting push-to-talk (PTT) communications through multicast channels to a plurality of wireless devices. The PTT server uses the unicast approach to deliver the PTT communication to a group of PTT clients when it does not have the location information of the PTT clients in the group. In one embodiment, the wireless devices report their location to a PTT server after receiving a PTT communication for a group and a timer is started. The wireless devices continue to report their location when moving from an area served by one base station to an area served by another before the timer expires. The PTT server also starts the timer for that PTT group with the same value after initiating the PTT group communication. The PTT server uses the location information to determine if multicast channels can be used when transmitting PTT communications to the wireless devices.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to communication in a wireless telecommunicationsystem, and more particularly, to the registration of locationinformation of individual wireless communication devices of a designatedgroup in a wireless telecommunication system.

2. Description of the Related Art

In wireless telecommunication systems, Push-to-talk (PTT) capabilitiesare becoming popular with service sectors. PTT can support a “dispatch”voice service that operates over standard commercial wirelessinfrastructures, such as code division multiple access (CDMA), frequencydivision multiple access (FDMA), time division multiple access (TDMA),and global system for mobile communications (GSM). In a dispatch model,communication between endpoints (“end user devices”) occurs withinvirtual groups, wherein the voice of one “talker” is transmitted to oneor more “listeners.” A single instance of this type of communication iscommonly referred to as a dispatch call, or simply a PTT call. A PTTcall is an instantiation of a group, which defines the characteristicsof a call. A group in essence is defined by a member list and associatedinformation, such as group name or group identification. A PTT groupcall generally comprises a PTT call with 3 or more group members. In theabsence of a wireless multicast channel, each group is formed by thecombination of separate point-to-point connections between each endpointand PTT server. Each endpoint is also known as a client. Alternatively,when a group is reduced to two members and a PTT call is from one memberto another, the PTT call would be a direct call between these twomembers.

FIG. 1 illustrates a prior art architecture 100 supporting PTTcommunications. The architecture includes the deployment of a single PTTserver 112 region in conjunction with a carrier's CDMA infrastructureand packet data network. Each region of the PTT server 112 is deployedover a specific portion of a carrier packet data network. The PTT server112 within the region may be routing traffic between one or more PacketData Service Nodes (PDSNs) in the carrier network. A communicationdevice 102 that supports the PTT feature is in communication with a basestation (BS) 104. Each BS 104 may be in communication with one or morebase station transceivers (BTS) 114. The base station 104 is incommunication with a high speed network 106 and PTT communicationsreceived from the communication device 102 is sent through the basestation 104 and the network 106 to a packet data service node (PDSN).The PDSN communicates with the high speed network 106 and a PTT server112's network 108, which is connected to a PTT network 110. The PDSNforwards the PTT communications to a PTT server 112 in the PTT network110.

The PTT server 112 handles PTT communications among members of a PTTgroup. The PTT server 112 receives a PTT communication from one memberand forwards it to all members of the PTT group. The PTT communicationis usually received as data packets from the network 110, and the PTTcommunication sent out by the PTT server 112 is also in data packetformat. A packet data service node (PDSN) and a connected base station(BS) then established through a BTS 114 a dedicated traffic channel totransmit the PTT communication to a receiving mobile client (a PTTmember).

FIG. 2 illustrates a prior art communication tower 202 connected to a BS104 and transmitting radio signals in its coverage area where severalwireless devices 102 are located. The BS 104 transmits a PTT calldestined for two wireless devices 102. When a user initiates a PTT calldestined to members of a PTT group, the PTT server 112 determines thelocation of each member and forwards the PTT call to each member. Whentwo receiving members of a PTT call are served by a single BS 104, theBS 104 establishes one communication channel to each wireless device. Ifthere is another incoming PTT communication to members of another PTTgroup in the same cell, the BS 104 needs to allocate resources andestablishes additional traffic channels to each of other receiving PTTmembers.

Allocating resources for each PTT communication and establishing atraffic channel to support each PTT communication are important part ofthe PTT communication system. It is desirous to have a PTT communicationsystem that can easily and efficiently manage the resources to supportmultiple PTT calls utilizing the specific location information of thevarious group devices.

SUMMARY OF THE INVENTION

The apparatus and method described herein enables efficient usage ofmulticast channels for broadcasting of PTT communication to a pluralityof wireless devices. In one embodiment, there is provided a method forregistering location information of a wireless communication device. Themethod includes receiving from the base station a push-to-talk (PTT)communication and, if the PTT communication received is for a groupcall, transmitting a location information to a PTT server.

In another embodiment, there is provided a method for transmitting PTTcommunications to a plurality of wireless devices through a multicastchannel. The method includes receiving a PTT communication destined fora plurality of wireless devices, identifying location information foreach of the plurality of wireless devices, checking if the locationinformation is valid, if the location information is valid, checking ifmulticast communication can be used, and if the multicast communicationcan be used, sending the PTT communication through a multicast channelto the plurality of wireless devices.

In yet another embodiment, there is provided an apparatus fortransmitting push-to-talk (PTT) communications on to a plurality ofwireless devices through a multicast channel over a wirelesscommunication network. The apparatus includes a network interface unitfor receiving a PTT communication destined to a plurality of wirelessdevices and sending the PTT communication to the plurality of wirelessdevices, a storage unit for storing location information for each of theplurality of wireless devices, and a controller unit for analyzing thelocation information and determining whether multicast channels can beused to transmit the PTT communication to the plurality of wirelessdevices.

Other advantages and features of the present invention will becomeapparent after review of the hereinafter set forth Brief Description ofthe Drawings, Detailed Description of the Invention, and the Claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a prior art architecture of a wireless communication network.

FIG. 2 a prior art base station supporting a PTT communication tomultiple wireless communication devices.

FIG. 3 illustrates a base station supporting a multicast PTTcommunication to multiple wireless communication devices.

FIG. 4 illustrates information exchange during a PTT process.

FIG. 5 is a flow chart for one embodiment of a wireless device process.

FIG. 6 is a flow chart for one embodiment of a PTT server process.

FIG. 7 is a block diagram for one embodiment of a PTT server supportingthe present system.

DETAILED DESCRIPTION OF THE INVENTION

In this description, the terms “communication device,” “wirelessdevice,” “wireless communications device,” “PTT communication device,”“handheld device,” “mobile device,” “mobile client”, “end-user device”and “handset” are used interchangeably. The terms “call” and“communication” are also used interchangeably, as are the terms “basestation” and “base station server.” The term “application” as usedherein is intended to encompass executable and nonexecutable softwarefiles, raw data, aggregated data, patches, and other code segments. Theterm “exemplary” means that the disclosed element or embodiment is onlyan example, and does not indicate any preference of user. Further, likenumerals refer to like elements throughout the several views, and thearticles “a” and “the” includes plural references, unless otherwisespecified in the description.

In overview, the system and method enables wireless devices of a PTTgroup of preferably three or more members to efficiently communicatetheir locations to a PTT server 112. It should be noted that the systemcan be implemented from an initial direct call between two members of aPTT group, where additional members are then added to the group.However, in an implementation as presented, a group call will be used tomean an initial PTT call with 3 or more users.

When a PTT communication is sent to a group of wireless devicesdistributed throughout a geographical region, generally onecommunication channel is established from a BS 104 to each wirelessdevice. The communication channel is a unicast channel since it is fromthe BS 104 to one wireless device. When multiple wireless devices arelocated in the same geographical region served by the same BS, the BS104 can broadcast the PTT communication through a multicast call. Themulticast call is supported by Broadcast Multicast Services (BCMCS). TheBCMCS allows optimized use of a broadband wireless network for deliveryof BCMCS content streams to one or more terminals in one or more regionsof an operator's network. The multicast call is then transmitted over amulticast channel. The multicast channel is commonly used when there ismore than one recipient in a particular geographical area. So, insteadof establishing multiple unicast calls, one to each recipient, amulticast call is established.

FIG. 3 illustrates a BS 104 supporting a multicast communication to twowireless devices, 402, 404. The efficiency usage of multicastcommunication is enhanced when the multicast communication is used tosupport a large number of wireless devices; however, for simplicity ofthe description, the example described by FIG. 3 is limited to twowireless devices 402, 404. As illustrated in the process 420 in FIG. 4,at 422 a member of a PTT group uses his wireless device to make a PTTcall to other members of his PTT group. At 424, the regional networkrelays the communication to the PTT server 112. The PTT server 112receives the PTT communication and determines that two members arelocated in the same geographical area and served by the same BS 104. ThePTT server 112 determines that it is possible to use a multicast call totransmit the PTT call to those two recipients. At 426, the PTT server112 first sends a call request to the targeted wireless devices via BS104. The call request contains information about the multicast channelto be used for this group call. At 428, the targeted wireless devicesobtain the details about the multicast channel using informationreceived from the call request message and also from the BS 104 overheadmessages. The targeted wireless devices then start to monitor thebroadcast channel. After the PTT call setup signals are exchanged, theoriginator starts to send speech to the PTT server 112, and the PTTserver 112 sends the speech with multicast traffic to the BS 104. The BS104 sends out the speech over a multicast channel.

To efficiently use the multicast communication, the PTT server 112generally needs to know the location of each wireless devices of a PTTgroup. However, tracking the position of wireless devices constantly maysignificantly increase the network traffic. By tracking the position ofwireless devices only when the PTT communications are likely to occur,the network traffic can be reduced. The PTT communications usually occurin a “burst mode,” i.e., after a first PTT communication is generatedfrom a user, it is likely that it will be followed by PTT communicationsfrom other users. This burst of PTT communications may last a fewminutes, and then may be followed by a relatively long period of silenceuntil a next burst. A typical scenario of this burst mode of PTTcommunications is as follows. A foreman picks up his wireless device andsends a PTT communication to his crew to inquire about the progress of aroof construction. After receiving this inquiry on a wireless device, amember of his crew responds through another PTT communication that thejob is progressing but there may not be enough shingles. The foreman,upon learning of this possible shortage of shingles, responds by tellinghis crew that he will go the nearest building supply store to pick upadditional shingles; the crew responds by acknowledging the receipt ofthe message. The acknowledgment is followed by silence that may last ahalf hour until the foreman arrives at the building supply store. Afterarriving at the building supply store, the foreman calls his crewthrough a PTT communication and inquires about the quantity of shinglesneeded to finish the roofing job. His crew responds through another PTTcommunication with the quantity needed, and the foreman acknowledges it.In this example, there are two bursts of PTT communications separated bya period of silence.

One way to track the positions of wireless devices without substantiallyincreasing the network traffic is to track the positions after the firstPTT communication. When the PTT server 112 receives the first PTTcommunication from a user, it is likely that the location informationfor each wireless device is old and no longer valid. Therefore, the PTTserver 112 sends the PTT communication to each receiving PTT memberthrough a unicast call, i.e., the traditional way of establishing acommunication from a BS 104 to each wireless device. Since, it is likelyfor the PTT server 112 to receive follow up PTT communications for thesame PTT group, it would be beneficial for the PTT server 112 to trackthe position of each wireless device for a certain time period.

FIG. 5 illustrates a process 500 in which a wireless device monitors andreports location information. In block 502, a wireless device receives afirst PTT communication as a group call from a BS 104. Generally a PTTserver 112 sends a call request to the targed wireless device via a BS104. Proceeding to block 504, the wireless device starts a timer. Thetimer may be of any type of device which may be used to track timeduration. Alternatively, a time stamp or similar type of time trackingmethod may be used. Proceeding to block 506, the wireless device sends amessage to the PTT server 112 with its location information. The messagecan be a registration message or any other message capable oftransmitting the location information. The wireless device constantlymonitors broadcast messages from the BS 104 and the broadcast messageincludes the identification of the BS 104. The identification of the BS104 received from the broadcast messages is generally stored. When theuser moves from one area covered by one BS 104 to another area coveredby another BS 104, the wireless device learns about the location changewhen the identification of the BS 104 retrieved from a newly arrivedbroadcast message differs from the identification of the stored BS 104.This identification of the BS 104 may be sent to the PTT server 112 andused by the PTT server 112 as the location information. Alternatively,the broadcast message sent from the BS 104 may also include a multicastregion identification, which can be used by a wireless device toidentify its current location. Any other identification information thatthe wireless receives, such as GPS, may be used to identify its currentlocation.

At block 508, the timer is checked to determine if it has expired. Thetimer may be used as a measure that the location information has becomeobsolete. The actual timer value is generally configurable and may varydepending upon the environment of the wireless communication network. Ifthe timer has expired, the location information is most likely notaccurate any longer and process 500 proceeds along the YES branch to anEND. In some configurations, after the timer expires, the wirelessdevice stops monitoring the location information until the timer isreset by another incoming PTT communication. Therefore, a PTT group callwill be received as a first PTT group call as stated above if thewireless device has not received a PTT group call for a predefinedperiod. For example, if a PTT group call is received after the timer hasexpired, this PTT group call will be considered as the first PTT groupcall. If the timer has not expired, the process 500 proceeds along theNO branch to block 509. At block 509, the wireless device checks to seeif a PTT group call has been received. If a PTT group call has beenreceived, process 500 proceeds along the YES branch to block 512, wherethe timer will be reset each time a PTT group communication is receivedby the wireless device. In this way, the wireless device continues toinform the server about its location for a determined period afterreceipt of each PTT communication. However, other configurations may notreset the timer when a PTT group communication is received. In yet otherconfigurations a value may be added to the timer value. Process 500 thenproceeds to block 510.

Returning to block 509, if a PTT group call has not been received,process 500 proceeds along the NO branch to block 510. At block 510, thewireless device constantly monitors if its location has changed whilethe timer is running. If the wireless device's location has not changed,process 500 proceeds along the NO branch to block 508, where the timeris checked for expiration. If the location has changed, process 500proceeds along the YES branch to block 506, where the wireless devicesends a message with new location information to the PTT server 112. Asindicated earlier, the location information may be contained within anytype of message ordinarly sent to the PTT server 112. Other embodimentsmay use specific location messages sent to the PTT server 112.

FIG. 6 illustrates a process 600 in which a server stores locationinformation. In block 602, a member of a PTT group uses his wirelessdevice to make a PTT call to other members of his PTT group. A PTTserver 112 generally receives that PTT call from the user. At 604, thePTT server 112 identifies the PTT members associated with the callrequest and retrieves information on each PTT member. Identifying thePTT members may be done through a user database that may consist of auser name, a user ID and other information associated with a user. Otherconfigurations may use other well known standards in the art to identifymembers. In one configuration, the PTT member information includeslocation information. In block 606, the PTT server 112 checks if validlocation information is available. If the location information is notavailable or expired, i.e., old location information may be disregarded,the process 600 proceeds along the NO branch to block 608. In block 608,the PTT server 112 sends the PTT communication as a group call to eachPTT member through unicast channels. The group call to each PTT membermay be any message which provides the functionality to alert a PTTmember that a PTT call is being requested. Proceeding to block 610, thePTT server 112 starts a timer. In some configurations, if the timer isrunning already, then it will be reset. Proceeding to block 612, the PTTserver 112 receives and stores the location information sent by eachwireless device. Any method known to send and receive locationinformation may be used. At block 614, the location information becomesobsolete when the timer expires and the process 600 proceeds along theYES branch to the END. In other configurations, the timer may be reseteach time the PTT server sends a PTT communication to the wirelessdevices. Therefore the process 600 proceeds along the NO branch to block612, where the PTT server will continue to receive location informationfrom the wireless devices for a determined period after sending a PTTcommunication. Alternatively, the PTT server 112 may, instead ofstarting a timer, associate a time stamp with each location information.The PTT server 112 can use the time stamp to determine whether thelocation information is recent or obsolete. Other embodiments may usewell-known data aging algorithms to determine whether the locationinformation should no longer be used.

Returning to block 606, if the location information is available andvalid, the process 600 proceeds along the YES branch to block 618. Inblock 618, PTT server 112 checks whether multicast calls can beemployed. The multicast calls can be used if two or more wirelessdevices are located in the same geographical area and served by onesingle BS 104. If the multicast call can be used, process 600 proceedsalong the YES branch to block 620, where the PTT server 112 sends thePTT communication to the PTT members through the multicast channel.Returning to block 618, if the multicast call cannot be used, theprocess 600 proceeds along the NO branch to block 622. In block 622, thePTT server 112 sends the PTT communication to the PTT members throughunicast channels. In both instances, sending the PTT communicationthrough the multicast channels, as shown in block 620 or unicastchannels, as shown in block 622, the process 600 proceeds to block 610and starts or resets the timer. By starting or resetting a timer, thelocation information will be updated with new location informationreceived from the wireless devices. The new location information mayaffect how new PTT group calls are transmitted to the targeted wirelessdevices. It is noted that a combination of multicast and unicast callsmay be used when the wireless devices are distributed in such way thatsome wireless devices are located in the same area while others aredistributed in different areas. For example, wireless devices A, B, andC are located in the same area and served by the BS 1, and wirelessdevices D and E are located in different areas and served by the BSs 2and 3 respectively. The PTT server will send the PTT communications tothe BS 1 with instructions for a multicast call to wireless devices A,B, and C. The PTT server will also send the PTT communications to theBSs 2 and 3 with instructions for unicast calls to wireless devices Dand E.

FIG. 7 illustrates a simplified block diagram 700 of a PTT server 112.The PTT server 112 receives through a network interface 704 PTTcommunications from wireless devices. A controller 710 checks a PTTcommunication and determine its recipients. The controller 710 retrievesfrom a storage unit 706 information about each recipient of a PTTcommunication. By checking the location information for each recipientand some other factors, the controller 710 can determine if multicastcalls can be used. If the multicast calls can be used, the controller710 sends the PTT communication with instructions for a multicast callthrough the network interface 704 to a receiving base station 104. ThePTT communication and the instructions are sent as a data packet througha network to the receiving base station 104, and then transmittedthrough a multicast channel from the base station 104 to the receivingwireless devices. The PTT server 112 may also include a timer 708 thathelps to determine when to store the location information received fromthe wireless devices.

In one embodiment, when a user, John, wants to use his wireless deviceequipped with a PTT feature to communicate with his crew, John activateshis wireless device. The wireless device sends a floor request to thePTT server 112. The PTT server 112 receives the request, verifies thatno other user has the floor, and grants the floor to John. The grantmessage is received by John's wireless device and John can then speakinto his wireless device. The wireless device transmits John's messageto the PTT server 112. The PTT server 112 receives the PTT message fromJohn, and identifies members of his PTT group. The PTT server 112retrieves the location information for members of this PTT group andsees that the location information is no longer valid since it was lastupdated on the previous day. The PTT server 112 then sends the PTTmessage to base stations with an instruction for unicast calls.

After receiving the PTT message from the PTT server 112, the basestation 104 transmits the PTT message as a group call through acommunication channel established between the base station 104 and thetargeted wireless device. The targeted wireless device receives the PTTmessage and verifies that it is sent through as a first group call, andthen proceeds to start a timer and send its location information to thePTT server 112. The wireless device will continue to send its locationinformation when the wireless device moves to a new location and thetimer is still running. The messages with location information from allwireless devices are received by the PTT server 112. The PTT server 112saves each location information with a time stamp.

After receiving the PTT message from John, Mary decides to follow upwith another PTT message. So Mary sends a request for the floor to thePTT server 112, which verifies the availability and grants the floor toMary. Mary speaks to the wireless device, which then sends the PTTmessage to the PTT server 112. The PTT server 112 retrieves the locationinformation of each wireless device and sees the location information isrecent and that David and Paul have the same location information. ThePTT server 112 then sends the PTT message with instruction for amulticast call to the base station 104 serving David and Paul. The PTTserver 112 also sends the PTT message with instruction for a unicastcall to the base station 104 serving John.

While listening to the PTT messages, David drives his car to anotherlocation served by a base station 104 that is serving John. David'swireless device realizes that it is being served by a different basestation 104 and sends a location registration message with new locationinformation to the PTT server 112.

After listening to Mary's PTT message, Paul decided to follow up withhis PTT message. Paul requests and receives the floor and speaks his PTTmessage to his wireless device. The PTT message device is again sent tothe PTT server 112, which checks the location information of eachtargeted wireless device. Now, the PTT server 112 sees that David andJohn are served by the same base station, so the PTT server 112 sendsthe PTT message with instruction for multicast call to the base station104 serving David and John. The PTT server 112 also sends the PTTmessage with instruction for unicast call to the base station servingMary.

Although the invention is described above in a PTT environment, theinvention is not limited to PTT communications. In a broader sense, thesystem and methods optimize bandwidth utilization by a base stationsupporting multiple multicast communications. In view of the methodbeing executable on a wireless service provider's computer device, themethod can be performed by a program resident in a computer readablemedium, where the program directs a server or other computer devicehaving a computer platform to perform the method. The computer readablemedium can be the memory of the server, or can be in a connectivedatabase. Further, the computer readable medium can be in a secondarystorage media that is loadable onto a wireless communications devicecomputer platform, such as a magnetic disk or tape, optical disk, harddisk, flash memory, or other storage media as is known in the art.

In the context of FIGS. 5-6, the method may be implemented, for example,by operating portion(s) of the wireless network, such as a wirelesscommunications device or the server, to execute a sequence ofmachine-readable instructions. Though the process is illustrated insequence, the method may be implemented in a different sequence or as anevent driven process. The instructions can reside in various types ofsignal-bearing or data storage primary, secondary, or tertiary media.The media may comprise, for example, RAM (not shown) accessible by, orresiding within, the components of the wireless network. Whethercontained in RAM, a diskette, or other secondary storage media, theinstructions may be stored on a variety of machine-readable data storagemedia, such as DASD storage (e.g., a conventional “hard drive” or a RAIDarray), magnetic tape, electronic read-only memory (e.g., ROM, EPROM, orEEPROM), flash memory cards, an optical storage device (e.g. CD-ROM,WORM, DVD, digital optical tape), paper “punch” cards, or other suitabledata storage media including digital and analog transmission media.

While the invention has been particularly shown and described withreference to a preferred embodiment thereof, it will be understood bythose skilled in the art that various changes in form and detail may bemade without departing from the spirit and scope of the presentinvention as set forth in the following claims. For example, thedescription above is based on an audio PTT communication, it isunderstood the apparatus, system, and method can be easily modified tosupport other type of media, such as video, data, etc. Furthermore,although elements of the invention may be described or claimed in thesingular, the plural is contemplated unless limitation to the singularis explicitly stated.

1. A method for transmitting location information of a wirelesscommunication device comprising: receiving from a base station apush-to-talk (PTT) communication; determining if the PTT communicationis a group call; and if the PTT communication is a group call,transmitting a location information of the wireless communication deviceto a PTT server.
 2. The method of claim 1, further comprising:monitoring the location information broadcast from a base station; andstoring the location information.
 3. The method of claim 1, furthercomprising: starting a timer upon receiving the PTT communication;comparing a newly received location information with a stored locationinformation; and if the newly received location information differs fromthe stored location information, sending the newly received locationinformation to the PTT server while the timer is still running.
 4. Themethod of claim 1, wherein the location information is an identificationof a base station.
 5. The method of claim 1, wherein the locationinformation is an identification of a multicast region.
 6. The method ofclaim 1, further comprising sending a registration message with thelocation information to the PTT server.
 7. A method for transmitting PTTcommunications to wireless devices through a multicast channel,comprising: receiving a PTT communication destined for a at least onewireless device; determining valid location information for the at leastone wireless device; identifying at least one wireless device capable ofmulticast communication; and sending the PTT communication through amulticast channel to the at least one wireless device capable ofmulticast communication.
 8. The method of claim 7, further comprisingcomparing a time stamp of the location information with a current timeto determine validity.
 9. The method of claim 7, comprising identifyingat least two wireless devices having similar location information to becapable of multicast communication.
 10. The method of claim 7, furthercomprising receiving the valid location information from the at leastone wireless device.
 11. The method of claim 10, wherein the validlocation information is an identification of a base station.
 12. Themethod of claim 10, wherein the valid location information is anidentification of a multicast region.
 13. The method of claim 10,further comprising: starting a timer; and storing the valid locationinformation while the timer is running.
 14. A system for transmittingpush-to-talk (PTT) communications to wireless devices through amulticast channel over a wireless communication network, comprising: anetwork interface unit for receiving a PTT communication destined to atleast one wireless device and sending the PTT communication to the atleast one wireless device; a storage unit for storing locationinformation for the at least one wireless device; and a controller unitfor analyzing the location information and determining whether multicastchannels can be used to transmit the PTT communication to the at leastone wireless device.
 15. The apparatus of claim 14, further comprising atimer for determining the validity of the location information.
 16. Theapparatus of claim 15, wherein the controller further being capable ofsetting the timer and storing the location information received from theat least one wireless device while the timer is running.
 17. Theapparatus of claim 15, wherein each location information furtherincludes a time stamp.
 18. An apparatus for transmitting push-to-talk(PTT) communications to wireless devices through a multicast channelover a wireless communication network, comprising: means for receiving aPTT communication destined to at least one wireless device and sendingthe PTT communication to at least one wireless device; means for storinglocation information for the at least one wireless device; and means foranalyzing the location information and determining whether multicastchannels can be used to transmit the PTT communication to the at leastone wireless device.
 19. The apparatus of claim 18, further comprising atiming means for determining the validity of the location information.20. A computer-readable medium comprising at least one instruction,which, when executed by a machine, causes the machine to performoperations, the instructions comprising: a set of the instructions toreceive from the base station a push-to-talk (PTT) communication; a setof the instructions to determine if the PTT communication is received asa group call; and a set of the instructions that when the PTTcommunication is received as a group call, to transmit a locationinformation to a PTT server.
 21. The computer-readable medium of claim20, further comprising: a set of instructions to monitor locationinformation broadcast from a base station; and a set of instructions tostore the location information.
 22. The computer-readable medium ofclaim 20, further comprising: a set of instructions to start a timer; aset of instructions to compare a newly received location informationwith a stored location information; and a set of instructions todetermine if the newly received location information differs from thestored location information, sending the newly received locationinformation to the PTT server while the timer is still running.
 23. Thecomputer-readable medium of claim 20, wherein the location informationbeing an identification of a base station.
 24. The computer-readablemedium of claim 20, further comprising a set of instructions to send aregistration message with the location information during transmissionto the PTT server.
 25. A computer-readable medium comprising at leastone instruction, which, when executed by a machine, causes the machineto perform operations, the instructions comprising: a set ofinstructions to receive a PTT communication destined for at least onewireless device; a set of instructions to determine validity of thelocation information for at least one wireless device; a set ofinstructions to identify at least one wireless device capable ofmulticast communication; and a set of instructions to send the PTTcommunication through a multicast channel to the at least one wirelessdevice capable of multicast communication.
 26. The computer-readablemedium of claim 25, further comprising a set of instructions to comparea time stamp of each location information with a current time todetermine validity.
 27. The computer-readable medium of claim 25,further comprising a set of instructions to identify at least two of thewireless devices having similar location information to be capable ofmulticast communication.
 28. The computer-readable medium of claim 25,further comprising a set of instructions to receive the locationinformation from the at least one wireless device.
 29. Thecomputer-readable medium of claim 25, wherein the location informationbeing an identification of a base station.
 30. The computer-readablemedium of claim 25, further comprising: a set of instructions to start atimer; and a set of instructions to store the location information whilethe timer is running.